Friction clutch unit

Abstract

A friction clutch unit with two coaxial friction clutches the first of which has a first friction disc driven by the crankshaft of an internal combustion engine and disposed between an axially fixed and an axially movable pressure plate. The second clutch has a second friction disc which drives the input shaft of a change-speed transmission in the vehicle which embodies the engine and is disposed between an axially movable pressure plate and an axially fixed pressure plate. The axially fixed pressure plates of the two clutches are connected to each other by a rotary housing which defines a fulcrum for a common dished spring having an outer region bearing against projections provided on the axially movable pressure plate of the first clutch and an inner region bearing against projections provided on the axially movable pressure plate of the second clutch in engaged condition of the clutches. The bias of the common spring upon the axially movable pressure plate of the first clutch is assisted by a dished second spring which bears against the outer region of the common spring and reacts against an abutment forming part of the housing. The second clutch is disengaged ahead of the first clutch and the first clutch is reengaged ahead of the second clutch by an axially movable shifting plate which is connected with the common spring radially inwardly of the inner region of the common spring. The outer region of the common spring pivots relative to the axially movable pressure plate of the first clutch during disengagement of the second clutch and the common spring pivots relative to the fulcrum during disengagement of the first clutch.

We claim: 
     
       1. A friction clutch unit, comprising coaxial first and second friction clutches each of which includes an axially fixed rotary pressure plate, an axially movable rotary pressure plate and a rotary friction disc between said pressure plates; a common clutch spring interposed between said clutches, as considered in the axial direction of the clutches, said spring having a first region bearing against the axially movable pressure plate of one of said clutches and a second region disposed radially inwardly of said first region and bearing against the axially movable pressure plate of the other of said clutches in engaged condition of such clutches, said spring further having a portion disposed intermediate said first and second regions; and a fulcrum defining a substantially annular seat for said portion of said spring, said spring being pivotable with reference to said seat. 
     
     
       2. The unit of claim 1, wherein said fulcrum is fixed, as considered in the axial direction of said clutches, said portion of said spring and said seat defining a clearance in the engaged condition of said clutches. 
     
     
       3. The unit of claim 1, wherein said spring has a first side facing one of said clutches and a second side facing the other of said clutches, said fulcrum being adjacent to one of said sides. 
     
     
       4. The unit of claim 3, wherein said one side of said spring faces the axially movable pressure plate which is engaged by said first region. 
     
     
       5. The unit of claim 1, further comprising means for disengaging said clutches, including a device arranged to engage said spring radially inwardly of said second region and to move said spring axially of said clutches in a direction to reduce the bias of one of said regions against the respective axially movable pressure plate. 
     
     
       6. The unit of claim 5, wherein said spring is installed between said clutches in prestressed condition so that said regions thereof normally bear against the respective axially movable pressure plates. 
     
     
       7. The unit of claim 5, wherein said one region is said second region and said device is arranged to reduce the width of said clearance to zero subsequent to said reduction of bias of said second region upon the respective axially movable pressure plate and to thereupon pivot said portion of said spring relative to said fulcrum in a direction to reduce the bias of said first region upon the respective axially movable pressure plate. 
     
     
       8. The unit of claim 7, further comprising additional means for biasing that axially movable pressure plate which is biased by said first region in engaged condition of the respective clutch. 
     
     
       9. The unit of claim 8, wherein said additional biasing means comprises at least one further spring. 
     
     
       10. The unit of claim 9, wherein said further spring is a second dished spring. 
     
     
       11. The unit of claim 10, wherein said second dished spring is arranged to bias that axially movable pressure plate which is biased by the first region of said common spring by way of said first region in engaged condition of the respective clutch. 
     
     
       12. The unit of claim 11, wherein said common spring includes a seat for said second spring. 
     
     
       13. The unit of claim 10, further comprising housing means defining an abutment for said second spring, said abutment being located radially outwardly of said first region of said common spring. 
     
     
       14. The unit of claim 13, wherein said abutment is fixed, as considered in the axial direction of said clutches. 
     
     
       15. The unit of claim 10, further comprising housing means defining an abutment for said second spring, said abutment being located radially inwardly of said first region of said common spring. 
     
     
       16. The unit of claim 15, wherein said abutment is fixed, as considered in the axial direction of said clutches. 
     
     
       17. The unit of claim 8, wherein said additional biasing means applies a force only against that axially movable pressure plate which is biased by said first region of said common spring in engaged condition of the respective clutch, the other axially movable pressure plate being biased solely by the second region of said common spring in engaged condition of the clutch including said last mentioned axially movable pressure plate. 
     
     
       18. The unit of claim 17, wherein said portion of said common spring and said seat define a clearance in engaged condition of said clutches and further comprising means for disengaging said clutches including a device arranged to engage said common spring radially inwardly of said second region and to pivot said first region relative to the corresponding axially movable pressure plate to thereby reduce the bias of said second region upon the corresponding axially movable pressure plate and to reduce the width of said clearance to zero, and to thereupon pivot said portion of said common spring about said seat in a direction to reduce the bias of said first region upon the corresponding axially movable pressure plate and to simultaneously reduce the force which said additional biasing means applies to the last mentioned axially movable pressure plate. 
     
     
       19. The unit of claim 18, wherein said device is movable in a first direction to disengage said clutches and in a second direction to engage said clutches, the movement in said second direction entailing pivotal movement of said portion of said common spring about said seat in a direction to increase the bias of said first region and of said additional biasing means upon the respective axially movable pressure plate, reestablishment of said clearance and ensuing pivoting of said first region relative to the corresponding axially movable pressure plate to increase the bias of said second region upon the respective axially movable pressure plate. 
     
     
       20. The unit of claim 1, wherein said portion of said spring and said seat define a clearance in engaged condition of said clutches, said spring further having a second portion located radially inwardly of said second region and further comprising means for engaging and disengaging said clutches including a device for moving said second portion of said spring axially of said clutches in a direction to reduce said clearance to zero while pivoting said first region relative to the respective axially movable pressure plate during disengagement of one of said clutches and to thereupon pivot said first named portion of said spring relative to said seat during disengagement of the other of said clutches, said spring having a first lever arm during pivoting of said first region relative to the respective axially movable pressure plate and a different second lever arm during pivoting of said first named portion relative to said seat. 
     
     
       21. The unit of claim 1, further comprising a crankshaft forming part of an internal combustion engine and drivingly connected with the friction disc of said first clutch, a second shaft forming part of a change-speed transmission and connected to and receiving torgue from the friction disc of said second clutch, and a flywheel including at least one of said pressure plates. 
     
     
       22. The unit of claim 1, further comprising means for effecting disengagement of said second clutch ahead of said first clutch. 
     
     
       23. The unit of claim 1, further comprising a second dished spring arranged to bias the axially movable pressure plate of said first clutch against the respective friction disc in engaged condition of said first clutch, and axially fixed abutment means for said second spring, said fulcrum being disposed between the axially movable pressure plate of said first clutch and said common spring, said second spring being disposed between said common spring and said abutment means, and said abutment means being disposed between said second spring and the axially movable pressure plate of said second clutch, as considered in the axial direction of said clutches. 
     
     
       24. The unit of claim 23, further comprising a rotary housing, said fulcrum and said abutment means forming part of said housing. 
     
     
       25. The unit of claim 24, further comprising a crankshaft forming part of an internal combustion engine and drivingly connected with the friction disc of said first clutch and an input shaft forming part of a change-speed transmission, said input shaft being connected to and receiving torque from the friction disc of said second clutch. 
     
     
       26. The unit of claim 25, further comprising bearing means rotatably mounting said housing in said crankshaft. 
     
     
       27. The unit of claim 26, wherein said housing comprises a cupped section confining the axially movable pressure plate and the friction disc of said first clutch, said fulcrum having an annulus of openings and the axially movable pressure plate of said first clutch having an annulus of projections extending through said openings and being engaged by said first region of said common spring in engaged condition of said first clutch. 
     
     
       28. The unit of claim 27, wherein said cupped section is rigid with the axially fixed pressure plate of said first clutch. 
     
     
       29. The unit of claim 27, wherein said fulcrum is rigid with said cupped section. 
     
     
       30. The unit of claim 29, wherein said fulcrum consists of sheet metal and includes an annular bead which defines said seat. 
     
     
       31. The unit of claim 27, wherein said housing further comprises a second cupped section which confines said springs, said second spring having a first region abutting against the first region of said common spring and a second region located radially inwardly of the respective first region and abutting against said second cupped section. 
     
     
       32. The unit of claim 31, wherein said second section includes a radially inwardly extending portion constituting said abutment means and disposed intermediate said second spring and the pressure plates of said second clutch, the second region of said second spring abutting against said portion of said second section. 
     
     
       33. The unit of claim 23, further comprising a ring-shaped seat interposed between said common spring and said second spring, the axially movable pressure plate of said first clutch having an annulus of projections which are biased by the respective region of said common spring in engaged condition of the corresponding clutch. 
     
     
       34. The unit of claim 1, further comprising a rotary housing, said housing including a first section rigid with the axially fixed pressure plate of said first clutch and confining the friction disc and the axially movable pressure plate of said first clutch, and a second section rigid with said first section and at least partially confining said common spring. 
     
     
       35. The unit of claim 34, wherein the axially fixed pressure plate of said second clutch is connected with said second section. 
     
     
       36. The unit of claim 35, further comprising means for axially movably connecting the axially movable pressure plate of said second clutch with said second section. 
     
     
       37. The unit of claim 36, wherein said connecting means comprises leaf springs which hold the axially movable pressure plate of said second clutch against angular movement relative to said second section. 
     
     
       38. The unit of claim 36, wherein said connecting means is disposed between the axially fixed pressure plate of said second clutch and said second position. 
     
     
       39. The unit of claim 1, further comprising a second dished spring for biasing the axially movable pressure plate of said one clutch in engaged condition of such clutch and a housing including abutment means for said second spring, said housing further including a portion which constitutes said fulcrum and said common spring having a plurality of openings, said abutment means including components extending through the openings of said common spring and connected with said fulcrum. 
     
     
       40. The unit of claim 39, wherein each of said components includes spaced-apart first and second radially extending portions respectively engaging said fulcrum and said second spring and an axially extending portion disposed between the respective first and second portions and extending through an opening of said common spring. 
     
     
       41. The unit of claim 1, further comprising means for actuating said clutches, said actuating means including said common spring and further including means for moving a portion of said spring axially of said clutches so as to disengage said second clutch ahead of said first clutch and to engage said first clutch ahead of said second clutch. 
     
     
       42. The unit of claim 41, further comprising a crankshaft forming part of an internal combustion engine and arranged to transmit torque to the friction of said first clutch, and a second shaft forming part of a change-speed transmission and arranged to receive torque from the friction disc of said second clutch. 
     
     
       43. The unit of claim 42, further comprising a flywheel including at least one of said pressure plates.